What's Different About North Korea's Latest Missile Test

North Korea's weekend launch of an intermediate-range ballistic missile further demonstrated that the country is consistently trying to come up with new, better ways to keep its nuclear deterrent reliable and safe from attack. According to North Korean state media, Sunday's early morning launch of a Pukguksong-2 ballistic missile featured a number of new features, including tracked launcher designed to take the country's nuclear weapons offroad where they are more difficult to detect.

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According to theRodong Sinmun, the official paper of North Korea's Worker's Party, the new missile is an adaptation of the submarine-launched Pukguksong-1 ("Polaris-1") missile tested last August, but is claimed to have an even greater range. Here's a video from North Korean state television with the missile and launcher in action:

Images released by Korean state media show that the Pukguksong-2 is a so-called "cold launch" missile that uses compressed air or some other gas to blast the missile upward from the launch tube. Moments later, the rocket motor fires and the missile goes on its way. This ensures the hot exhaust doesn't destroy the launch tube, which can then be reloaded with more missiles.

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According to Pyongyang, the missile uses solid fuel as opposed to liquid fuel, a major technological improvement. Due to the corrosive nature of liquid rocket fuel, many older missiles are stored with their fuel tanks empty. This also means that, once fueled, a missile must be de-fueled within hours so that its fuel tanks are not permanently damaged. Fueling a missile takes hours, during which time the missile, launcher, and payload are vulnerable to attack. Also, if the missile is separated from its fuel trucks, it can't launch.

Solid fuel, while much more complex, allows the missile to be fueled once at the factory, after which the missile is ready for action for years.

Pukguksong-2 launch vehicle.

Then there's the launch vehicle. Previous North Korean mobile missiles such as the Musudan use launcher vehicles based on Chinese heavy transport vehicles. Pukguksong-2, on the other hand, uses a tracked launch vehicle with running gear similar to that of the P'okp'ung-ho main battle tank. The launcher's road wheels, as well as their positioning versus the front idler wheel, look identical to the P'okp'ung-ho. The vehicle chassis has been lengthened by the addition of two more road wheels per side, to accommodate the weight and girth of the missile.

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The decision to go tracked may be derived from the fact that the Chinese vehicles—which may have entered the country illegally—are no longer accessible. Another factor may be that the entire country has only 500 miles of paved roads, limiting how far a wheeled vehicle can travel to hide from South Korean and American surveillance. A tracked vehicle can go on rougher, unimproved roads, and even offroad if necessary. That having been said, ballistic missiles are notoriously delicate and cannot stand too much jostling over bad terrain. One example was the SS-15 missile, nicknamed by NATO the "Scrooge":

How far can Pukguksong-2 go? It's probably too early to tell. According to South Korea's Joint Chiefs of Staff, the missile had an apogee of 344 miles travelled 313 miles before splashing into the Sea of Japan. That isn't enough to calculate a range—it might have been blown up prematurely—but it's likely that, fully operational, the missile could reach American bases throughout South Korea and Japan. The missile is almost certainly unable to reach the continental United States.

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According to Korean state news, the missile test not only proved the cold launch system and reliability of the solid fuel system—the warhead successfully separated from the missile before the flight ended. The report from Pyongyang also mentions the missile having an "interception evading" feature, to prevent the warhead from being shot down in flight. The report doesn't mention any details of this, but typically such features, often called "penetration aids" include spewing radar-fooling chaff, a decoy warhead, or radar jammers.

North Korean leader Kim Jong-un has invested enormous resources into his country's nuclear deterrent. Sunday's launch shows that Kim is serious about building a credible nuclear deterrent to keep his enemies at bay.

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